Buffett has always favored businesses with durable economic moats. In the health insurance space, the idea of a moat is reinforced by and industry dominated by just a few major players -- with UnitedHealth being the largest among them.

UNH stock soared after Warren Buffett’s Berkshire Hathaway revealed it bought shares of the healthcare company. Nonetheless, UnitedHealth faces a long list of unresolved issues.

Berkshire Hathaway just disclosed that it dumped $1.6 billion into a sinking ship, and Wall Street instantly paid attention.

Warren Buffett's Berkshire Hathaway built a $1.6 billion stake in UnitedHealth last quarter, marking one of its last wagers with the investor as CEO.

Warren Buffett's Berkshire Hathaway has acquired 5 million shares in UnitedHealth Group , a regulatory filing showed on Thursday, sending the health insurer's stock up 7% in extended trading.

In this video, I will go over the second-quarter activities of 12 super investors -- which stocks they bought and which they sold. I'll be talking about Warren Buffett, Bill Ackman, Chuck Akre, Howard Marks,